Just crunching the numbers to see if my suspicion was true or not...

2005 - 42 - (13 Transformers - 12 Convention, 1 membership, - store excl) (29 GIJoe - 28 Convention, 1 membership)
2006 - 43 - (16 Transformers - 12 convention, 1 membership, 3 store excl) (27 GIJoe - 22 Convention, 1 membership, 4 store excl)
2007 - 43 - (12 Transformers - 11 convention, 1 membership, - store excl) (31 GIJoe - 26 Convention, 1 membership, 4 store excl)
2008 - 50 - (20 Transformers - 12 convention, 1 membership, 7 store excl) (30 GIJoe - 25 Convention, 1 membership, 4 store excl)
2009 - 48 - (15 Transformers - 14 convention, 1 membership, - store excl) (33 GIJoe - 29 Convention, 1 membership, 3 store excl)
2010 - 48 - (18 Transformers - 15 convention, 1 membership, 2 store excl) (30 GIJoe - 25 Convention, 1 membership, 4 store excl)
2011 - 43 - (17 Transformers - 14 convention, 1 membership, 2 store excl) (26 GIJoe - 24 Convention, 1 membership, 1 store excl)
2012 - 43 - (18 Transformers - 15 convention, 1 membership, 2 store excl) (25 GIJoe - 24 Convention, 1 membership)
2013 - 61 - (22 Transformers - 15 convention, 1 membership, 6 subscription) (39 GIJoe - 25 Convention, 1 membership, 13 subscription)
2014 - 63? - (24? Transformers - 15? convention, 1 membership, 1 store excl, 7 subscription) (39 GIJoe - 25 Convention, 1 membership, 13 subscription)

(Three Minicons I counted as 1, and Kreon packs I've just counted as 1)

Not the gradual increase I was thinking it was. 2005 was a big increase for them for taking on the TFs license, and then in 2013 was another big surge with the Subscription series boosting their non-convention exclusive numbers.