How much manga content is there? When could the anime potentially reach a roadblock?
Manga is up to chapter 140. This was chapter 38. If a year is in between the end of this anime 2 cour, the current arc will be concluded. You could fit possibly two 26 episode seasons in there.
Math is 140-38+42 (If a 2 cour starts next season - 10 the day weeks we've had of my hero academia season 2) divided by an optimistic 3 comic chapter pace.
144/3
is 48 episodes. And that is if they kept a pace of 3 episodes a piece, which isn't likely.
So two full seasons of 24-26 episodes each is likely possible after this season is over, without them running into a roadblock.
I realize someone might point out the year after as well, but anime productions can be ran up to a year before a season's release, so I'm not going to add in two 52 week years.