3.5mm can support dual dac?
2.5mm is support dual dac
but 3.5mm is not support dual dac

can support 3.5mm dual dac after f/w update? or can't support?
The 3.5mm output works with a single DAC only.
We can make the 3.5mm SE output with Dual DAC, or Single DAC.
But, it's an HW design choice, and we need to choose one of them and design the HW.
As we checked the audio performance and battery consumption of both options, the single DAC option provides the almost same performance as dual DAC, while saving more than max. 6~7 hours of battery time.
Thank you!

What kind of battery life can you expect with a pair of IEMS with 16 Ohm using the 3,5 mm jack?

I saw the numbers on the spec site was based on AAC, but what if you use APTX HD or LDAC? 
Yes, the battery times across each BT codecs are different.
AAC works at the lower bitrate and consumes lesser power than the other codecs.
That's the reason why every maker specifies the battery time with the AAC codec.

Please check the link below for more information:

It's a simulation result, but there wouldn't be much difference with the real world battery time.
We'll update the full specification of battery time for each codec and use cases, once we fix and confirm the final HW design.

Please note that QCC512x consumes only half of the power than CSR8675 while providing doubled processing power with quad cores.
Assumed with similar HW conditions and use cases, 5K QCC5124 would deliver the best power efficiency and longer battery time than others.

Thank you!