As far as I know, not.
Well, the highest count of Variables I had in a Map was about ~450.
Variables also take up minimal space ~60 = 1kb or something.
No mapper has ever used more than 1000+ variables in his map. But actually there are no limits to the number of variables or each type of variable, be it 1000+ or even 100,000+ variables but it could make finding each variable tough and causes (i think) lag when it's waaaay too much and a significant increase in filesize....
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.