with composites in this critical part is asking for trouble.
My thoughts exactly.
If they want to be super modern and ground breaking then creating a wing design that does not need to sweep to allow takeoffs from reasonable length runways, but also high dash speeds would be much more impressive...
There haven't been that many changes in wing design... taken to the very core... the straight wing of WWII like the Yak-3 subsonic planes was standard, with sweeping it back of the wing necessary as speeds approached the speed of sound as with the MiG-15 and 17. The MiG-19 achieved supersonic speed with a straight swept wing but with an extreme sweep which increased takeoff and landing speeds so the delta wing and tail surfaces of the MiG-21 tried to mix reasonable runway length with supersonic speed with a shorter runway... then they went for exotic solutions like solid rocket boosters to shorten takeoff run and of course lift jets for STOL and VSTOL, and at the same time swing wings. The swing wings prevailed but were not the ideal solution, which came in the form of the MiG-29/Su-27 wing and lifting body shape to allow short take off and landing with supersonic speeds.
In bombers they went from swing wing back to subsonic in the flying wing design...
Cold is not a problem for composites are they have been used for decades on planes that take off in 40C and operate at -40C.
Not all parts of an aircraft are subjected to outside temperatures in flight... the fact that the F-35 has problems operating in the cold in Japan suggests that operating in the Arctic at much much lower temperatures would be a serious problem...
I understand the west is happy to build enormous air conditioned and heated hangars for their planes... the Germans keep their tanks in tents to prevent them getting too cold too, but that is just not practical in Russia. They might be building the hangars but there are times when the aircraft will spend time sitting outside for whatever reason so they have to be able to take it.
If they had the wing box tooling available, I would agree, just build it. But since they don't and have to fully reconsider this structure, for 3 units a year composites, may offer an opportunity, or Al Li, or a combination of composites, alumunim and steel.
They have built a new factory to make Tu-160s from scratch which includes a forge to make the titanium centre structure. I would expect a forge that size will be able to be used to wield other materials as well... the justification for building it was because they are going to build another 50 odd Tu-160s and such a forge could also be used in the construction of the PAK DA as well... and I suspect a new MiG-41 might benefit from one piece large section Ti structures being formed in one piece...
Even steel has vastly improved in 40 years. Point is, replicating the old structure is just as, or maybe even more complex then just designing a new one from a clean sheet with the 40 years of additional knowledge they have.
Obviously they will revise the design.... if they didn't it would have been in mass production 5 years ago, but they needed to digitise the design and then upgrade it... they did it the way they did everything else... upgrade existing bits as far as possible while working on a major upgrade... and in the back ground work on the from scratch replacement... ie T-72 upgrades, T-90AM, and T-14.
Except with the White Swan you end up with Tu-160M, Tu-160M2, and PAK DA.