It's an important consideration to think through.
Buy bitcoin now. Don't wait for scaling solution to end because the price of bitcoin will definitely grow after successful upgrade.
You can compare it to Litecoin - After SegWit signalling ended price of LTC skyrocketed, it will be the same with Bitcoin.
I don't think Slark fully grasps all of the consequences that could come from the fork. It's not about whether bitcoin will go up or down, it's about where you keep your bitcoin and whether you'll be shut out (or not) from the alternative bitcoin version that could be created as a result.
Segwit could still result in two bitcoins.
A safer alternative to exposing yourself now would be to spend your investment on Ethereum or Litecoin. Both have been relatively more stable than Bitcoin and Litecoin could even see another pop up to the $100 mark this summer.