Boosts Purchased Before 30 Carried Over To Pre-Season?

So, I underestimated how many XP boosters I would need to hit level 30. I have over 50 win boosters left and am wondering if I will get them back when pre-season hits, so I don't have to buy more to level up past 30 with the new XP system? I am asking this because once you hit 30, you can no longer see the boosts, assuming I still have them. But I'm worried they just get deleted and won't be carried over. This is over $10 USD of boosts I have. I know it's not a lot, but I'd like to not just have my $10+ just thrown away.

Of course if there isn't a system in place to let people keep their boosts that are either invisible or deleted once hitting 30 for pre-season, then I completely understand. Just want to know if I will get the boosts back once pre-season hits. Thank you for your time in advance!

Also, sorry if this is in the wrong section. I couldn't really find a more suitable section than gameplay, so I put the thread in here. If it is in the wrong place, may a moderator move it to the right section or notify me? Thank you.