No, I think Sony will not ban those who upgrade after having tried jailbreak although I would still format and system restore just to be safe
. I reckon they might ban users who go on PSN without upgrading as if it fills up with cheaters as it certainly would , and gets a bad name because of that it will ruin years of thier work.
I predict they are hoping to lock down security on all new games so jailbreak users have no way of playing any games released from now on they hope to make users want to upgrade by showing them what they are missing, new games, 3d movies, all PSN games, I bet eventualy in a year at least 50% would change thier mind or buy second ps3 if playing new games was impossible.+ add the fact we cant go online as its another major reason for people to upgrade and go legit.
Think about it, if they BAN people who are upgrading thier FW and buying games they are only screwing themselves, thats what they want, people to upgrade, if they ban upgraders they will only scare others who might have been thinking about upgrading, I reckon they are definitly hoping to squash this by trying to make people want to upgrade.
Also look at PSP PSN, no bannings and loads of hacked PSP's online for years. they dont want to ban you cos that means you and your PS3 are no longer a potential customer , besides its also bad for buisness to be doing negative things like mass bannings, bad press and it draws attention to the fact that thier console is hacked, lots of people out thier never heard of psgroove, the masses just update without question and on grand scale of things it might be fairly small percentage of people who actually stayed on FW3.41 and hacked thier PS3
But that might change if an open source downgrader comes out... or even CFW!