No 50+ gamers I know either use smart phones or consoles for gaming, well some use consoles. Smart phones suck for gaming, no tactile feel from virtual buttons.
I was thinking the same thing but I tend to create a large compressed backup file and upload that instead. My backup file is currently under 100 gigs, the most critical files not my whole system's files. If I backed up my gaming account (I don't need to since I use Steam Cloud) and compressed it, it'd probably only be another 50 to 100 gigs. This way I should never hit the 5 million file limit.
Having said that, I feel 5 million files is too low for a lot of people.