If by 2nd generation CCR perhaps you mean The tilera 1.5 Ghz CPU variants? I would think mikrotik finally learnt how to cool the CPUs rather than having to modify the CCR to get superior cooling and silence.
The CPUs are simply not equal in IPC performance for networking. In terms of architecture if running at the same clocks, core, etc the fastest MT has is PPC, then TILE, then MIPS, then ARM. ARM is actually slower than MIPS but the ARM routers come with more cores and frequency than MIPS. The order only changes when more complex tasks are given such as QoS which ARM will do faster than MIPS.
The ARM architecture used doesnt really affect the performance that much. Linksys was getting 1Gb/s using ARM A7s while other premium routers were using broadcom ARM A9 which couldnt do 1Gb/s with PPPOE as networking in a simple way doesnt require out of order processing as the tasks are all streamlined but when you have QoS and other complicated processing than things change.
I went around looking and didnt see any new SoC or CPU from tilera that would seem like something MT would use in the CCR unless they are bringing out even higher end products that have many more cores to handle 10x more bandwidth but that would be unlikely as it would cost so much.
I bought the CCR1036 when it came out so i have an early variant which i modified and have changed the PSU. heres a picture with the chip model visible
The fans in the picture werent the ones i used for the CCR, i used scythe fans instead. If you search through Tilera that already is the best tile-gx SoC they offer so unless MT is moving to another type of Tile CPU but there arent any suitable variants for use in the same range that is newer. Very likely MT will just fix the flaws from the first generation of CCRs such as the crappy PSU and cooling and lack of non networking IO and probably include faster ram (tile-Gx SoC states 1866mhz DDR3 and MT is using 1333mhz DDR3).