I wouldn't do this. You highly underestimate the probability that they will find some cause to fire you for. If they look hard enough, they will find one, or else they will simply make one up that will be hard for you to fight in court. Have you ever delivered something late? Has there ever been a single bug in your code? Have you ever disagreed with someone of higher rank in a meeting publicly? And I do mean "ever", over the entire time you've been at the company; they can pull whatever they want, whenever they want (it's happened to me).

Here's the thing: If your company will only give you a 6% raise as a Principal Engineer, and you're doing the work of 8 people, the company is probably not doing well financially. If they furthermore have to lay off multiple Senior Engineers, they're probably doing really poorly financially; you don't lay off talent. This company is a sinking ship and you're doing well to get off it. Your friends will also do well to get off it, and the economy isn't as bad for engineers as you think it is; it's horrible for retail and service industries, but I'm getting tons of recruiter calls on LinkedIn these days, it's not that bad. If your friends get laid off, they should be able to find another job fairly easily and quickly, and conversely there's no way to know that if you "take the fall" as it were that it will even save any of their jobs.

Just keep on stroking. Do what you plan to do: Collect your bonus, collect your stock options, and leave as planned.

Here's a thought: If you have seniority at the new company, can you ask HR at the new company if you can bring some friends with you? People in authority tend to have some leeway to hire people they have confidence in and know to fill out their team, and maybe you can use some of your newfound seniority to help your friends from this company, if that's something you want to do.

First, look after yourself.

If your colleagues are laid off, and then you give notice, there are two possibilities: Either your employer says "oh ____" and has to scramble to hire your colleagues back; at that point your ex-colleagues will have very strong cards in their hands and if they are clever, they will benefit (guys, feel free to post here :-) ). Or your employer doesn't try to win them back, in that case you couldn't have prevented the layoff. So doing nothing is much better for you, but likely better for your colleagues as well.

IMHO, you got to look for the number 1 - you.

I would NOT suggest to say anything before all your cards in play.

It is not your job to safeguard this employer from bad faith damage he did to you and going to do to other senior engineers

As you stated, its been a year and a half since you cared for this employer :)

I think your post is quite long, so first I want to summarize it to the essentials.

1. Soon you will leave your current employer for a position elsewhere.

2. You have been told that soon some other employees will be laid off, some of them are friends of yours.

3. By announcing/hinting early that you are leaving you can prevent that (some) of those other employees will be fired.

To be honest, I think point 3 is a pretty bold assumption. You probably are a good engineer/employee if your current company wants to promote you and you get a good offer from another company. However do you really do the work of an entire 8-person team ? And even if that would be the case, does your employer share that opinion ?

So my advice is not to announce/hint that you are leaving beforehand. It is far from certain that that will save the jobs of your colleagues/friends.

If you tell them that you're planning to leave by a certain date, then that's the equivalent of a voluntary resignation.

And if they fire you early, you may still be owed severance (or even owed unemployment benefits), but you may only be owed money for the period of time between the time you got fired and the actual time you said you'd leave, or perhaps, you may even get nothing.

At least, that's the way I think it works with unemployment benefits. Here is a passage I found for for California EDD (see section C). Not knowing your state, I just picked California.

Now perhaps your severance package works differently. And also, you may be able to negotiate with your employer a situation where you quit and they allow you to get your severance package. But if you're indeed much more competent than the other software engineers they want to lay off, that's really going to be a hard sell.

And if you're in a union, your collective agreement may allow you to take the place of someone less senior who's getting laid off, but based on your profession, I really doubt that you're in a union.

In any case, be careful with this. Personally, I don't really know the law, and I haven't read your contract, but I wouldn't take the risk of announcing my departure.

Also, I would not underestimate your COBRA health insurance payments. Those can be pretty significant since you have to pay for both your share and your company's share of the premiums.

And a 12 months severance is not that bad, your laid-off colleagues may actually like receiving such a payout.

The unfortunate reality is that all you really stand to gain by giving advance notice is a good recommendation from your current employer in the future. You have much more to lose.

A good manager would appreciate the advance notice and work to secure your final bonus, but this may or may not succeed depending on the overall company financial position, your company policy, your manager's boss's opinion of you and so on. Importantly, many managers would either not work to secure your bonus or actively block you from getting it.