No one really knows. Before August 1st the first stage of uasf there probably will if everyone assumes that bitcoin will go up. I'm thinking this is when we will see $4000 bitcoin or higher, but after that bitcoin might crash back down to $3000 where it will stay for a while. Altcoins are probably entering a bear market now that bitcoin is getting some improvements and more attention. By November bitcoin could hit $10000 and alts will probably be on average half of what they are now on a red day.
Yap as to there are no past reference on btc so we better just have to wait on whats gonna happen. But in my speculation it would only affect the btc transactions. And if there were any effects then most would be in a positive ways. A lot of problems have occured since the price went up and segwit is the one best solution for this kinds of problems. So we just have to wait and avoid some high transaction fees for now.