But it actually depends. Right now the 1MB block size can do just fine with the amount of volume we have. If the volume skyrocketed for some reason, as we saw with the stress test, the whole thing became a mess (confirmation times taking hours, blockchain.info not opening up.. etc). It would collapse.
So basically, we need it pretty soon because you never know when things can go trendy and mainstream and one has to be ready for that. Here's what Gavin proposes which includes an estimation of what would happen if we stay at 1MB blocksize:
Seriously? 1 Petabyte? for a Blockchain size?
I'm wondering, can I use a Bitcoin core in the future? Because it would take a long time to download the Blockchain
Don't you love the overly dramatic green failure line coming from the one mb threshold. rofl