You know I think you're right. I used colleagues evo's with 4g and to be honest I'm not impressed with the speed.
The theoretical max of 3G is 7.2Mbps. I astonish people in that I can hit NEAR 5 at home, I've never heard of anyone scraping anything above that. So I'm with ya there, 4G will probably perform well below it's theoretical speed, I've heard some say more so than 3G. (By comparison, if you look at most Speed test websites they say the average 3G user clocks in at just under 1mbps, so that's 1/7th of it's theoretical max!)
I also heard Leo Laporte mention on one of his podcasts an excellent, excellent point about 4G. 3G is starting to get plagued more and more by smartphone users sucking down massive amounts of data from the same tower. Basically, bandwidth being tapped out. I dunno about you guys but 3G is useless in very populated areas for me, like at the mall for instance. I was trying to pull something up in the parking lot, full signal. Worthless. Ran a speed test, wopping 85kbps downstream. So then, what Leo was saying is, what makes us think 4G will be any better? It's still shared bandwidth, and at first it will be great because only a handful of people will have it, but soon they all will and anywhere populated it becomes very tapped out.
I should mention that I live near St.Louis, and in the City of St.Louis, any cell carrier will do. However, outside of the city AT&T is king. All of the others strictly cover the interstates, and barely branch out at all, and almost none of them have decent 3G. Sprint, for example, stops 20 minutes out of the city and goes to EDGE and stays that way. AT&T offers 3G over almost the entire state, including the VERY rural areas. Therefore, since most folks often have a reason to be out of the city, (like myself who lives an hour outside the city in a rural town) the VAST majority of St.Louisans (in my experience) use AT&T. The exception would be friends of mine who live in some of the suburbs right outside the city, or in downtown itself (then it's Sprint or T-Mobile usually). Anyway, point being, where I live may be an extreme example of bandwidth overload, but I still think 4G isn't going to be all it's cracked up to be.