Yes you can upgrade a regular MS908 later to a MS908Pro by purchasing a MaxiFlash Pro and pairing it to the MaxiSys. A) you are not going to gain any further free update subscription time for your Maxi Sys Tablet by doing so. B)You will not gain any further capabilities for your MaxiSys , other than gaining Autel Server access to programming files for BMW and Mercedes .C) Once you have paired the Maxi Flash VCI to your MaxiSys  and it becomes a Maxi Sys Pro there is no going back to a regular Maxi Sys.  The updates for a Maxi Sys Pro now going to cost hundreds of dollars more than for update subscription than a regular Maxi Sys. D) you still have to use the Maxi Flash VCI off a laptop and purchase an OE subscription and OE program to do any J2534 device required programming for anything else  other than BMW and Mercedes. After your update subscription expires , your access to Autel server for BMW and Mercedes programming files likely ends . If it were me (rarely needing mercedes or bmw programming),  would probably not pair the MaxiFlash to a MaxiSys and just use it strictly off my laptop with a 24 hour OE subscription when the need for programming arises.