I guess the "new mikrotik powerline device" you mention means a simple USB charger, with the specialty that it is capable of letting through already-converted Powerline Communications (PLC) protocol data between its USB port and the 230V plug. This is the only way I could imagine this new feature which, by the way would only make sense if you already own a mAP and this additional "special" power supply (microUSB-230V) is cheaper than purchasing a standard PL7411-2nD (which already has WiFi and an Ethernet port on board).
Ultimately I believe both the mAP and the PL7411-2nD are essentially the same in terms of:
- They share the same main board including the QCA9531/9533 SoC
- They both have the AR7420 Powerline controller chip (which was not on the mAP's specs page) that does the actual Powerline protocol (PLC) conversion i.e. it converts and modulates 802.3 Ethernet data onto the 5V power pin
- A 230V to 5V power supply that is compatible with the powerline protocol i.e. it lets data (already powerline protocol) through between its 5V and 230V side
- and the difference is that you can have these in one single box as a PL7411-2nD or separately as a mAP + this "special"/"supprted" USB power supply. This is my understanding based on the current info and datasheets available.