There are several way of getting 3G or 4G internet access.
1. Tethering as you suggest.
2. Dongle.
3. MiFi.
These are very similar but using a MiFi gives you wifi to several devices.
The biggest problem is data cost. Landline alowances can be 10GB/month to 'unlimited' with overrun permitted, but dongles and MiFi tend to be 1GB to 3GB. Overuse is very expensive and sometimes is limited to a few hundred megs. Tethering costs vary a lot, I have heard that contract phones have very limited tether allowances. Dunno about 4G, no experience yet.
The other 3G/4G problem is variable access. You may get oodles of bandwidth at some times and none at others because priority has to be given to voice calls. In theory 4G will cure this by adding bandwidth, but use for tv will soon soak this up.
An unexpected problem is auto transmitter switching causing connections to drop out. I had near perfect operation until they added a mast and I got switched to and fro. 3G was ok but the theoretically better hsdpa dropped me completely. I gave up and am now a happy landline user (but I only plug in the voice phone for outgoing calls).