With the current network protocol being set up to support the existing win98 enabling file size any immediate changes would impact on client compatibility so the battle plan is to launch the new client and when folks are happy that its able to support the network and its users etc the developers can simply add a larger address size field in a new protocol packet thus ensuring there is no potential issues with the old client and no problems accessing larger files in the new.
With a general field size upgrade anything that may rely on it such as the file hashing will also need to be updated so theres a need to create another new packet to deliver the new hashes and also further packets to facilitate those that are going to impacted on due to the size field however in the source code its not a lot of work to add further new packets that are simply upgrades of an older one and over time such older packets can be retired from usage.
A lot of research has been done to look at file transfer handling and how best to secure it and make it more efficient but the priority to date has been to create a client base on which to add any enhancements so its unlikely the initial release will have such file transfer size enhancements in place but thats not to say it wont if the developers have time to do so.
In short then, the developers aim to lose the limitation but at the time of this asking that particular upgrade is not yet in place
