As long as Shepard is back they can call it whatever they want 😃
All joking aside, I don't know why Andromeda got such a bad reputation (as a game), if they didn't drop the ball and gotten all the bugs fixed and continued the series it is a great game as a spin-off.
Saying that, they can not continue ME4 as part of Andromeda as 600 years apart would probably mean all the original characters are already dead.
Yes Liara was about 21 in ME1 which would make her 621 if they continued the storyline of ME:A , Wrex was around 1400 already in ME3 and the rest can't live that long anyway.
I would rather they continue the ME game as part of the original series (we still have the creators of the reapers to deal with) and leave ME:A alone.
If they can continue ME:A and make ME:A2 I would love that, as there is so much to learn there and another ark to look for.
So my own opinion would be, leave ME:A make ME4 the continuation of ME3 (with a few years past, as they had to search for Shepard I bet).