Replace battery or replace MBP?

It’s tax return time!
My (mid 2012) 15” rmbp’s battery needs to be replaced. I don’t know whether I should just do that and save money OR

If it’s worth it to put that $200 towards a new machine. I’d be able to get almost $400 for trading in my computer and an additional $200 for trading in my iPad Air 2.

I really like the touch bar and considering stepping down to the 13” for portability.

I’m not sure what type of performance difference to expect from my current model to a new one.

I’d like to upgrade to a 512 SSD. My main needs are for some light video editing- currently using iMovie but would like to upgrade to final cut at some point. Other activities are light gaming and some photoshop.

I have no idea how long I’ll be able to get somewhat decent value for my current machine. Been looking at apples refurbished 13TB. I’m tempted to wait for Apple to bring quad core to the 13” (do I even need it?) but worried about what they would charge.

Any advice or perspective would be greatly appreciated, thanks!