Knowing my psychology, I would still get Pathfinder and I will most likely continue it because of the following:
Reasons for Pathfinder over GameMastery modules
1) Since I already paid for this, the product is "free" (plus with the discount, much of the product is actually free). I'm more willing to spend "free" money on something I'm not sure I will get full use of.
2) Since I already have more campaign ideas (and pre-published one I want to run), I'm not sure how useful more adventure paths will be to me - especially at a faster rate than I can run them. I also am quite happy with the campaign settings I have.
3a) I'm going to be buying GameMastery modules anyway since even with all of my campaign ideas and adventure paths made from various pre-published modules, I always need filler adventures.
3b) I won't intend to buy every GameMastery module, but when confronted with each, I'm imaginative enough to create a use for each of them and therefore justify to myself buying every single one.
4) I like Paizo and want to give them money.
Therefore, I'd use my transition credit for Pathfinder assuming I won't get as much use out of them, but still wind up buying each month's GameMastery module.
Reasons for continuing Pathfinder subscription after transition credit
1) I like Paizo and want to give them money.
2) I will think Varisia is cool and inspiring, so I'll either use it or incorporate much of it into the other settings I run (this being said even with little info out there - I just know myself, I get excited over "cool, new things" pretty easily).
3) Even though I have a ton of campaign ideas, I'm fickle and will postpone some to run the Pathfinder paths. At the very least, I would want to run them *someday*.
4) I want them to publish more of my stuff, so I should stay current.
5) I like Paizo and want to give them money.
Therefore, when the credit starts to run out, I'm sure I'll keep subscribing to Pathfinder even if I haven't run a single adventure or used a single article out of the first path.
So that's my thinking. Certainly not rational (i.e. why not spend my credit, which is real money, on the products I'm more likely to use?), but my brain am what it am, and that's all that I am.