@TaliaParks summarized all the upcoming troops very helpfully here: The (Un)Official Console Weekly Event Thread Part 1 (Closed)
He doesn’t break down exactly how many traitstones will be necessary, but it does list the upcoming troops and what colour of traitstones they need. Trying to guess at which ones people are most interested in is probably not worthwhile. Also, who knows how the developers are going to handle the next two months?