s there hope for adsl and wifi to be fixed in the future?
Because I stayed between stock operating system and openwrt.
Is it possible to solve the problem of Broadcom drivers one day?
Or should I stick with the stock OS?
ask Broadcom, we don't own any crystal balls ...
personally I think the chance of it ever getting supported is less than zero.
Golden rule: If you cannot change it, Leave it!
Stay away from non-open-source products if you want FOSS support!
Get yourself Openwrt supported router, they are many (and could be relatively cheap)
Short answer: No.
If you want a device with supported xDSL modem, your options are very limited. In reality, you can only go for one of the Lantiq chipsets and to the best of my knowledge there is only one "modern" device with OpenWrt support: AVM Fritz!Box 7520/7530. The older xrx200-based devices are still working fine, but are getting outdated in terms of performance.
Your next best solution is what @saladin said: Configure your DSL modem to bridge mode and use another OpenWrt router behind it.