AW&ST (Ares) has an SDSR
rumour page up and running. Not much on it, more asking than telling....
".....In that environment of secrecy, this blog will look at some of the talking points which may feature in the SDSR. It should not be taken as fact however, but more of an analysis of rumors, statements and information which has come to light in the last few months. It’s up to you, the reader, to give us kudos if our suppositions come true or indeed throw your thoughts into the mix."
Remark in the comments section that the 8 Merlin airframe upgrades are essential/associated with the ASAC/Crowsnest programme.
MPA/MMA - they're not sure if there will be an order, a completion or a statement of future need.
ISR/ED3 - Both open depending on the above.
"Aviation Week is confident that the Shadow will be retained in the SDSR and Britain will hang on to its Reapers until they are replaced with 20 examples of the certifiable model Reaper purchased under the Protector program.... The future of the Sentinel is far less certain however and much depends on the choice of a maritime patrol/multi-mission aircraft......
Also unclear is the future of the U.K.’s E-3D Sentry...... One suggestion is that if the U.K. invests in the P-8, it could also look the 737 AEW&C solution, because of the commonalities between the airframes."
Typhoon - they reckon they will get the additional 2 squadrons
"The Tranche 1s would be retained for U.K. air defense, training and as red-air aggressors for other units. First evidence of this was the recent transfer of Tranche 1 jets to the Falkland Islands in the South Atlantic in September 2015, six years after the first four aircraft were sent down there. Rumor suggests that 30 of around 50 Tranche 1 aircraft will be retained. The biggest challenge for the Royal Air Force will be manning the squadrons however."
F-35 - Pure guess work.
"The secrecy around Britain’s F-35 plans has been a tough nut to crack.......the U.K. defense ministry is currently planning for 48 aircraft for now. However some rumors suggest even this number could fall further and would support the carrier strike capability only..... Whether the SDSR 2015 will provide more clarity on the F-35 plans is unclear, after all, by the time of the next report in 2020, the aircraft will have only just achieved its U.K. initial operating capability from land, based on current timetables."
Helicopters
"Britain has heavily invested in its helicopters during and since the Afghan conflict, so it is difficult to see what changes the SDSR could bring about. Conceivably, the SDSR could impact the numbers of modernized Apache attack helicopter planned. Current planning is for 50 AH-64E-model aircraft down from 65. It could potentially revise plans for the U.K.’s fleet of 60 CH-47 Chinooks, some critics have suggested that the U.K. now has too many Chinooks.......
Defense officials could also retrospectively upgrade some of the eight EH101 Merlin anti-submarine helicopters that were not upgraded to Mk.2 standard. "