It'd help if you could list your full system specs. If your goal is to hit 144hz, a very strong CPU is usually needed.
1070 is a good upgrade for a 290 user, especially at FHD.
As for Vega. With rare exceptions, AMD usually undercuts Nvidia so you can wait and try to get a 1070 equivalent for less, or a faster card for the same, or for 1070 price cuts in a possible price war. But we don't know when Vega is coming, and even if it's soon we don't know if they will have a 1070 competitor right away (could target higher only at first).
My crystal ball is hazy, all it can tell you is price-to-performance generally increases over time so make a decision based on your willingness to get better performance now or later.