Nothings changed but the fact that Ash is battling Hala soon could change things. If he wins, that may very well mean he'll be leaving Melemele soon and won't have an opportunity to get Rockruff. Especially assuming he gets Litten.
I know Ash could get two captures within a few episodes, but still...
I imagine the school will act as home base for Ash. Spend some episodes on one island, and then return to the school before heading out again. So I think there are plenty of opportunities for him to get Rockruff.