At some point the monorail cars (and possibly track) will be too old. According to Wikipedia the monorail cars were built for the 1986 World Expo. The Cable Car is also from a similar date although I believe it's been like Triggers Broom with so much of it replaced over the years.
The monorail was refurbished in 2008, but even still, I do agree that the monorail either needs to be removed completely (and use a system similar to what's used in the Walt Disney World car parks, for example), or receive a major refurbishment. However, looking at the way Merlin is currently operating, I fear that it's more of a case of "Yeah, that's working fine right now lets wait another 5 years or so until it REALLY needs to be refurbished". The Alton TLC scheme claims that the monorail will receive some TLC over the next closed season, but I still believe that it will not be to the extent that is really needed.
The skyride was last refurbished in 2009/2010 and is still running fine in my opinion - my guess would be a refurbishment in at least a decade from now (providing that it doesn't burn down again).
The problem with a new entrance being built by Galactica is that it would be inserted right in the middle of Forbidden Valley, rather than a location with a nice backdrop of the Towers. Sure, it's more convenient for car park users, skyride users, and has a better location in general, but it just seems wrong that it's plonked between two major rollercoasters with no 'buffer' between the entrance and the major areas of the park.
I personally think that we will see a large scale dark ride for SW9. I think it could a) be in Cloud Cuckoo Land and encompass a retheme of the area, b) be built in the Air carpark, and possibly involve splitting FV into two different areas (Future theme and current FV theme), or c) replace Rita - by the time SW9 supposedly opens, Rita will be 17 years old. As it is, the ride hasn't got the best of throughputs, is a mediocre ride (especially compared with many recent launch coasters), and doesn't fit the area very well in general. Both CCL and the Air carpark have been earmarked for potential development at this stage.