I am not sure since when the Phaser Lances' description included the mention of a wide beam setting, but can we take it for granted now that saucer separation is incoming?
Because if that is the only upgrade you are giving the ship, we dread jocks will be mightily disapointed.
You can't put a several minute console ability on a fundamentaly broken ship and say "yes its fixed now." - please don't go that route.
Just go the sensible, non-moronic route: upgrade all fedeartion cruisers to match the mobility of th klingon cruisers.
You do not need to give them all DHC's, just give them the turnrate, and rework the modus operandi of beam arays (instead of 4 pulses over several seconds, change it into slow firing hammer blows, 1 shot every 4 seconds. Adjust the damage accordingly. this will fix all troubles base stat wise.).
As far as I know, there are no upgrades to the Galaxy-X planned.
The proposed saucer seperation ability that would cause the Lance to become a shotgun-like weapon was placed on indefinite hold due to code/art problems that also cancelled the Galaxy pack that many people were waiting for. There has been no further word on this, and so we can only say that work is probably been put on the back burner in favor of newer ships and content projects.
Also, if there were an upgrade of any kind, it would likely be in the form of a T5 Fleet Shipyard version that would require 5-6 Fleet Modules and feature increased Hull points and maybe one more Engineering or Tactical console, similar to the Fleet Excelsior and Fleet Assault Cruiser. However, the fact that there is the on-hold work with the Galaxy Pack in existence probably will also indefinitely put off the introduction of this kind of ship due to the need to incorporate the ability to use the non-existant Seperation ability from the Pack into it in the same way the Galaxy-R console can be used in the Fleet Galaxy.
In short, it is very unlikely any sort of upgrade or additional version of the Galaxy-X will be seeing the light of day anytime soon.