Given the time skip that occurs at the end of The Last Problem, and considering the Pillars are of varying ages, do you guys think that Meadowbrook is still around, or would she have passed on, as Mistmane and Starswirl probably would have?

Probably a bit older

Meadowbrook seems to be the youngest of all the pillars, so I'd say there's a pretty good chance she's still around by the time of the time skip.

7234698
Very true.