It will be a completely new interchange, not an adaptation of the existing one. On that stretch 4 tunnels might also be built, each between 200 and 800 metres, by covering the road where it is now. A side effect of them is a new dump for building waste (demolished buildings, etc). When I saw some plans on a public presentation (no way to take photos) it seemed that at least one of the ramps of this junction will be in one of the four tunnels (maybe as a separate bore).
I used the temporary junction once, as well as the one on Lugano north branch (
Swiss Geoportal). It was when AlpTransit made possible a visit with a round trip by bus in the southern half of the new rail tunnel, with the return part on the A2.
Another half-junction (only to/from the south) will be built here between Bellinzona north and south:
Swiss Geoportal
I saw the new <24> red diamond on signs leading to the Mendrisio-Stabio autostrasse.