I'd be pretty keen to correspond with you, OP, or other "senior" / experienced (30s, 10+ years) developers in NYC trying to skill up and get into higher salary positions, or at least share some experiences and intel. email is in my profile.
I'm in my 40s with 20 years experience in NYC. Applied to a handful of positions, but was politely turned away. I suspect age is a factor, but of course no way to prove it. I'm considering shaving 10 years off my resume and see how that goes. I've done management successfully but it was stressful, and I went back to development.
To beef up my list of skills, I'm starting to expand into areas that are natural progressions from my current set. For example, I use C# and Asp.Net for backend work, so I began using .Net Core; I use React on the front end, will add Redux; MySql/SqlServer for the database, will start working with Postgres; AWS for the cloud, will research Azure.
I'm not sure if I should be adding a whole new bullet point, such as learning Erlang/Elixir, Python/Django, Ruby/Rails, or something completely different.
Right, I am revising my resume currently, and for the first time I'm considering dropping off my earliest jobs - both because they were a long time ago, and because what I was doing then is more or less completely irrelevant to what I would want to be doing next.
My thought, looking at the senior developers around me, is that adding whole new bullet points is good.