I'm a product generalist at Meta and I've been offered to opportunity to ramp up to Android and possibly specialize in Android dev. What are the considerations I should be thinking about when 'switching tracks' like this. E.g. will this reset my progress towards promotion as a prodgen or will it enhance my skillset for future opportunities?
First, I recommend this discussion around figuring out your track and overall career direction. The other resources I link in my response there should help as well.
I think Android is a great place to be, and there's ample scope to grow on that track both within Meta and across the industry as a whole. I'm biased of course given that I've been doing Android for almost a decade, but even when viewing it more objectively, I 100% believe this. Some quick reasons why Android is awesome:
That being said, I'm also sure that being a product generalist is in the same boat where you could craft an incredible career out of it, both at Meta and in general.
What are the considerations I should be thinking about when 'switching tracks' like this.
Literally only one, especially since you're already working at Meta: Do you enjoy it? Your career already has a very good floor due to the prestigious FAANG company on your resume. Your goal now is to maximize your ceiling, and that pretty much requires finding something you genuinely enjoy. With Android, you can try building a side project app and seeing how that feels.
will this reset my progress towards promotion as a prodgen
It depends on how far you are towards E5. E4 -> E5 is the promotion where I generally see engineers develop more fundamental skills that are very applicable anywhere like project management, leadership, effective communication, and of course, being able to learn quickly. If you are on a good path building up those skills (usually E4 EE), you won't be set back too much as that will carry over. If you're on the earlier side of E4 where the value you add is mainly from raw technical proficiency, you will be set back a decent amount.
If you end up deciding on going into Android, here's my in-depth thoughts on how to get awesome at it.