It probably never will be.
As many of the answers correctly note, the bandwidth itself is adequate for many uses. It's not actually good enough for several applications, however, and as more people hop on 4G networks, the speed is going to vary even more -- as will latency / ping time -- making the following apps work even less well than they already do:
Really low-latency apps: the most salient example is probably online gaming, which won't tolerate triple-digit ping times
Higher-bandwidth streaming: Streaming Netflix on your phone or tablet works because the bitrate is low for the small screen. To get HD or even near HD quality on a larger screen requires sustained high bit-rate throughput. In theory, LTE allows this. In practice, the variability of the bitrate makes this awfully challenging
But neither of those is the killer, the killer is bandwidth limits. Data plans are typically capped at 2-5GB before rapidly increasing in price. Most of you use 20GB-200GB per month on your landline. In the U.S., no provider would even allow you to use this much bandwidth on an LTE connection regardless of your willingness to pay.
Over time, bandwidth needs are only going up, spectrum is more and more constrained, and while providers will likely allow slightly more data usage per month. the limits will not rise anywhere near as quickly as average bandwidth consumption.
Of course, as many answers suggest, if your needs for data are small and mostly mobile and you just don't want landline broadband, you can get by, but this is not some kind of cost savings or increase in convenience. You'd have to change habits, limit use, and probably pay more. Verizon just rolled out an LTE serivce for homes called HomeFusion in Dallas, Nashville and Birmingham. It's a separate sub from the LTE data on your phone, gives you 10GB and costs $60 per month, for example. No market I could find doesn't have a cheaper, better DSL and/or cable alternative (although certainly some addresses might be unable to get serviced, which was ostensibly the point of this offering).