I have a 2012 Nissan Maxima SV with 121,000 miles. 

The transmission is showing some signs of decay, or at least I think so. When going at slow speeds the car will sometimes sway forward and back, as if the acceleration is stuttering. This lasts for roughly a second or maybe two before it returns to normal.

When accelerating fast from 0, the car will sometimes display "BRAKE" for the parking brake on the dash. This is an error from when the drive belt broke but was since replaced. I think the dash error is related to the transmission. The parking brake never actually comes on and this may just be an unrelated glitch on the dash.

Carfax values the car at 4,500$(ish) while a transmission replacement would cost 5,000$(ish). 

The mechanic i go to is unsure how long the car will last. Soooo, the question is....

Should I look into selling the car now or wait for it to break down completely? I don't think the transmission is worth replacing.

I need a car that can last, at least, one year. Is it possible that my current vehicle can do so?

I posted a previous question asking about prices on trucks, which would be my option if I did sell my car. 

However, if the car can last for a year then I do not want to sell it. Beyond the stuttering issue, the car seems fine overall. Everything but the engine and transmission has been replaced already.