The absolute minimum transaction size(1) is for single input single-output transactions. They are 192 bytes each, 182 if transaction combining is aggressively used. 1MiB/10minutes * 182bytes = 9.6tx/s
Ok, let's go with 9.6 tps. That means roughly 25,000,000 transactions per month. If Bitcoin becomes a payment backbone where users transactions are reconciled monthly, the current blocksize limit supports 25 million users. I strongly dislike hard forks, so until we have several million users, the blocksize needs to be left alone.
When the user is in serveral millions, it is even harder for a hard fork. Actually, that is almost an event that may kill bitcoin.