If latest cockpit design would be significantly different from the last generation, pilots would have problems to change between the two, which would either limit the types they are allowed to fly (with all the organisational and financial impact) or it would create new risks.
You're, perhaps, forgetting history. In 1985 I was flying a very, really basic B732. The BY boys will remember. Then we became the lead airline for B767. Wow; this was a quantum leap. Fortunately we had a very strong pilot orientated Flt Ops management right up to MD level. They expected the pilots to be able to fly these new toys with the same competence as B732. We took it to some similar places; i.e. very basic Greek island airports = night circle to land at Corfu, or Kos or Heraklion etc. No problem. The culture was correct. My point is that such a mega change happened without a/c falling out of the sky and without the training department collapsing.
Most important is that the pilot fully understands the systems in his aircraft and works with them, not against. A pilot which is not trusting his systems should not fly that aircraft.
So how did we achieve this safe transition? Firstly the ground school was very thorough. The FCOM's had been simplified & diluted and CBT introduced. But, this was backed up at the end of every day with 'chalk & talk' FAQ's with a FE. During the CBT we used the sim as an FTD to explore and experiment with what we had learned that day. We came out with a healthy knowledge. We then went on the line and plugged in the automatics at 400' and watched what the a/c did; how it wanted to fly. We tried all the different methods via AFDS and learnt in depth how to fly & manage this new beast. The LTC/TRI/TRE's had a real indepth understanding and passed it on. When possible we hand flew it as that was the culture of the company. We'd learnt from the automatics what was necessary and then we applied it manually. Job done.
I then went to an airline who transitioned from B727 to B757. I took my BY philosophy with me, but had a culture clash. They insisted in a complete change and it became a "follow the FD" type operation with full automatics. The older guys flew it manually, but the newbies didn't know how and switching off the VNAV for descent planning was scary. Switching off the FD for departures from small empty airfields or approaches was even more so. Switching off the ILS on a CAVOK day was the final straw for some. All this was 25 hears ago.
I now fly B738 and HAL has sporned and migrated onto that fleet as well. I still fly my way and try to encourage others, but the ice is too thin and they don't want to venture out. OFDM is watching and they are afraid. When some do 'have a go' it might be a mess. They have a confidence blip and complain they don't get enough practice. True. I also teach TQ and they never had the skills in the first place via the syllabus. Hand flying on the line is discouraged and strict SOP's cause a trained monkey mentality. They know only a fraction of the capabilities of both the a/c and the systems.
You can only "trust your systems" if you understand them. Guys fly the a/c using the A/P looking only at the FD. It will always be centred, even when you stall or hurtle into the ground. It tells you nothing and can mask the truth of what is happening, i.e. attitude and V/S. In todays automated dependant operation the basic instrument scan, to confirm the FD is giving healthy guidance, is no more. It wasn't taught, save the raw data ILS, and it not used on line due to fully automatic operations. What chance have they got when the missing skills are needed? The way EASA is going I do not hold out any hope. Keep everything as cheap and as simple as possible just to be inside the safety envelope. Enough. Perhaps the days of single crew 99% automatic flight is not that far away. I'm sure the companies would love it. Any faults and the computer tells you how to fix it. That's not always a success if the computer is at fault. Bit like asking the police to conduct the enquiry into the police. The independent pilot needs to sort out the mess and decide if the computer solutions are correct: if not take over and save the day.
Ah, but that takes us back to the beginning and the circle is complete, or rather the spiral.