HTC does have a plan to work around this. They have developed what is being called a "technical update" which is different than the OTA updates that you might be familiar with. HTC needs EVO 4G LTE owners to test out this process. Consider it a little like the soak tests that Motorola does before a software update. If you're interested in being among the first HTC EVO 4G LTE owners to have Android 4.3 installed on your phone, you can send an email to them at HTCTrial@htc.com.
The HTC EVO 4G LTE will turn only two in June, but with a dual-core Snapdragon processor under the hood and only 1GB of RAM on board, this update will almost certainly be its last.