The currently running version of DD is indeed the 100th update to the beta.
That must be including silent updates, since you don't do more than one update per week and you miss weeks on occasion. We're still quite a ways from the 2-year mark of the beta.
EDIT - it's been 91 weeks since the beta started (roughly) so if you've currently hit 100 then you've averaged 1.1 updates per week. That seems about right if we count hot-fixes and silent updates, but as players we don't have clear visibility on those so we really can't count them.