Upgraded from performance plus to Extreme Pro. Account shows the new speed and customer service in India says it's effective immediately.
I still see old speeds after restarting my cable modem, my router, cleared cache and cookies.
I am testing from my hardwired PC connected via ethernet to a Netgear CM600 which is capable of 960 Mbps
edit: it started working a few hours after I posed this (note that I had previously re-booted my modem as I said originally) I am not seeing anything above 375 Mbps so far however
or do a factory reset which will reprovision.
No it won't sorry.
Upgrading speeds now will just waste your money. I am lucky if I have the speed I am supposed to have before the stay-at-home orders. And since they started I barely have 1/20th of my 100Mbps on a regular basis. If you reset your modem, disconnect the cable from the wall, everything they will tell you to try when you call, it may recover to 1/10th for awhile. Calling and having them tell you to do all that again while they do a reset on their end will get your speed back for a short time but half the time by the time I have finished filling in the survey and saying thank you for recovering my speed it has dropped again already. And it is not just the network being overloaded at a certain time of day. This happens at all hours, I am up at 3am and it still runs like every house in my neighborhood must be streaming their favorite shows during a zoom meeting while facetiming their online classrooms.
The modem will receive a new configuration file upon re-registration. Sorry if I was too colloquial; you're correct that the modem will not affect Comcast systems