Originally there was going to be a new Q before 2010. However that plan got shelved. The current M is nearly the same size as the last generation Q (its just 2 inches shorter and is the same width and height) and it has more interior space. Feature wise in terms of passenger comforts you can also get everything (and more) that the last Q45 offered in it. Currently the M which I happen to think is a fantastic car in may ways, is acting as the companies flagship sedan. The Nissan Cima and President have been discontinued and the Cima is what the last Q was based on. When the new M came out a VP
for Infiniti Global said something about them being open to bring back the Q and that some markets were asking for it, it would depend in part on how many fully loaded M's were sold. The Q however was never a big seller in North America which is probably a big part of the reason its been gone from the line up for so long.
I think it sold poorly for a few reasons, brand recognition. Where I grew up we didn't even have a dealership for Infiniti in our province for example I remember when my father got one a lot of people didn't even know what the heck it was. I don't know how common dealerships were in the USA. Secondly the Q while a great car was never really going after the fully loaded flagship S-Class or 7 Series, which is fine but I think if they do bring it back they need to really hit the ball out of the park. The other question is, what type of flagship does the brand need? Does it need a sedan or a great sports car?
The mind, like a parachute, functions only when open.