While Tkachuk is a great player and certainly does have a fairly unique style of play, he is certainly not a generational talent - let's get that out of the way right now. He has exactly one season of 100+ points. A generational talent is often used to describe someone like
Sidney Crosby who is the model of consistency or Alex Ovechkin for his legendary goal scoring prowess. Both Crosby and Ovechkin are the past generational players, the current generational players are
Connor McDavid (obviously) and
Auston Matthews, who appears to be this generation's Ovechkin.
Cale Makar and Andre Vasilevskiy are two other players at their position that you could make a case for slapping the "generational" tag on them.