just buy a MIFI or hotspot your phone, theres no reason for integrated LTE connections in laptops due to the abundance of other connectivity options.
That's exactly it. There are a few of us who would like the convenience and robustness of just going up where the Wi-Fi is and connecting to 3G/4G/LTE (personally I'm not a fan of some of these new hotspots that don't support legacy technologies, what if you're out traveling with no LTE? 3G or even EDGE is better than nothing). But it's just not likely to be a big seller. Anyone who would need to be online on the go would likely also have a smartphone, and most of those are capable of tethering. And of course, there are personal hotspot devices, USB dongles, etc.
However, I think if Apple did do it, they could do it like they used to do Wi-Fi. When Apple first started using AirPort (their Wi-Fi solution) they didn't include it on every computer. They left it out to save cost, even on the notebooks (few people used it at first, Wi-Fi technology wasn't as common as it is now). However, on every Mac, from the (later) iMac's and eMacs, to the PowerMac and the various Apple notebooks, had the capability to have Airport added. With most models, the antennas were already installed, and there was a PCMCIA laptop card slot (even on the desktops), which you could use to stick a $99 AirPort card into to enable Wi-Fi.
Apple could do the same with the MBP, they could simply add an inexpensive cellular antenna into the display (where the AirPort antenna is) and leave a 'slot' open internally for the addition of the cellular radios. I actually kind of wish they still handled airport the way they used to, because you could ALSO easily upgrade your Wi-Fi internally. With Wireless AC around the corner (draft devices already for sale) it'd be nice if I could just swap my Wireless N airport card with a Wireless ac airport card (It certainly doesn't need to be as big as the old AirPort cards).
However, I don't see Apple doing it. It's a niche product. And again, I'm torn on whether or not I would honestly buy it. I'd like it, yes, but with an AT&T Mobile Share plan tethering is included free so I can already tether with my iPhone, so... what's the point?