It's impossible to be 100% sure in crypto. As you say though, previous rises have had alts taking over as soon as bitcoin slows and starts to stabilise. This rise has been going on for a while, but bitcoin is still leading the way. We will see what happens, but the past is only ever a rough guide, it doesn't have to happen again. Personally I think we will have an alt run, but I'm probably about 70% sure.
are you talking for this year?
if this year maybe it will happen near the turn of the year, it can even happen next year in the peak of altcoin growth. we must see the dominance of bitcoin trading decreasing, and altcoin must increase trade.