The reason for doing a smaller number of episodes per season is (at least based on their previous interviews) due to the time it takes to produce the episodes. If they want 14 episodes to end the show, they can't make 14 episodes for season 7 because they barely had enough time to shoot 10 episodes in a year.
There is also a conflict between HBO wanting to extend the life of the show since it is so successful vs. the showrunners wanting to end it quickly (which I think to be honest is partly due to burn-out on their part, rather than purely creative reasons). And of course both sides face the reality of not being able to keep actors around forever.
A while ago the showrunners said they wanted seven seasons while HBO talked about 8. I guessed that we might get a 7A and 7B compromise, which is essentially what a short season 7 and short season 8 amounts to. Despite the showrunners insistence I wouldn't be surprised to see season 8 made longer or spread across 2 years though.
In any case I just hope it is able to do it justice. Personally I'd be a bit more concerned about an overly short run to the end than a longer one - I think the ship has sailed in terms of the show being short enough, but it could still end up too short.