Avril's only 27. If she continues to release albums at the rate she does, she might fit in two more albums before she's 90! They'd have to sell 35 million each. So yes I do think she can do it
The only ones I can think that will reach 100M album sales in nearest time would be Britney first then Adele follow ups would Gaga? but that would take very long unlike Britney obviously.
Adele will obviously sell a half of her album sales of 21 by her next, maybe she can sell a 10M at least so that's already a 40M album sales total of her