I would like to see this feature, but it's complicated. As @ryan.lutz says, printers all heat up at different rates. Not only does your brand of heat element play a factor, but also the firmware used on the printer itself. Namely most firmwares I know of (if not all) use a PID algorithm to heat up the element, depending on your hardware, what PID settings you have calibrated, the temperature of the element to begin with, and the temperature of the environment outside, you will get drastically different heat times. I believe you can get a ballpark figure, though.
This is something that could get implemented on MatterControl itself, but I think it makes more sense that this be something built into the firmware instead. It would also keep track of heating times even when your printer through SD and not through MatterControl.