Can more than 1 block be solved per 10 mins on average (LONG TERM)?
someone /could/ throw a lot of hash power into the system. and until such a time as the difficulty adjusts, they /could/ produce more blocks than one per 10 minutes on average. but difficulty will adjust after one or more 2016-block chunks (note that change in difficulty is capped at a factor of 4 for each 2016 block chunk), until once again even with the new hash power only one block per 10 minutes is produced on average.

so "in the short term" it is possible for someone to produce more blocks than 1 per 10 minutes, but "in the long term" unless they continue adding hash power perpetually, the difficulty will catch up to them.