I definitely think getting 4.5 inch out of service completely would be a good move - otherwise the T45's are carrying all the support burden for six mounts in service. Replacing it with a 127mm mount would likely be more complex - and therefore costly. I've certainly spoken to at least one RN sailor in warfare who was enthusiastic on that possibility.
Either way, getting Sea Ceptor cells onto Type 45 seems like a good move and will strengthen it's already good AAW capabilities.
I'm suspecting Type 83 will end up being a much larger ship than type 45 - the assigned number points at a multirole vessel and the 45's are already regarded as cramped for space in terms of upgrades etc. I'm thinking 12-14 thousand tons standard maybe ?
Having re-read the comments over the last 2 pages, I think I get what you guys are getting at (
RE: T45 / Mk8 vs BAE Mk110 vs BAE Mk45)
I have to say that I firmly believe that Type 45's will never be 'up-gunned' to the Mk45, as IMHO it'd be a waste of money. Similarly, while I believe the Mk110 to be a 'great gun' (
due to RoF / Munitions types that are now available), again IMHO, it would be a waste of money retro-fitting Type 45's with it.
Having made those x2 comments, I have to provide the thinking that drives them.
#1 - Mk8 / MOD1 4.5 Inch does give 'bang for the buck', as the RN already has a copious amounts of munitions, spares & crews that are trained to keep the guns going.
#2 - These guns / associated ships are going to be around for another 15 years minimum, so it makes sense to keep them until the end, rather than trying to 'cross-deck' the retro fitted Mk 110 / Mk45 into their replacements.
#3 - Costs saved by NOT integrating the newer guns, allows for funds to be spread out across the fleet, to incorporate the same new weapons into the new hulls as they come on stream, limiting initial expenditure into manageable chunks.
As for Type 83, simply not enough detail out on the interewebs for anyone to really hazard a guess, although I speculate that T83 will be greater than 10,000 GRT, probably heading for 12,000 GRT. The Type 26 hull form can be easily expanded by inserting a 10 - 15m long plug, allowing for additional prime mover power / more bunkerage, to go further, while giving the adaptability to possibly extend the Hangar /mission bay complex that Type 26 currently has.
I also feel that larger ships with smaller crews will be one of the key principles of Type 83, as there will likely be a drive to more automation of 'systems' that service the ship (i.e. not weapons systems, but hotel services / fluid control/HVAC & the like).