There is nothing to suggest that they are or are not taking action on this matter already.
..but not with any urgency. There is no question that they could easily have closed off the current "entry points" with minimal risk, and minimal need for testing, but the fact that many weeks have gone by and hundreds of units shipped since they must have been aware shows that it is not a high priority.
No one should be surprised, or annoyed, if FLIR do release a new 'hardened' build version of the E4. An ASIC based countermeasure would likely be enough to make life very difficult for a user to enhance their unit.
There would be no need for any hardware change. There are multiple things they could do on the existing
hardware to lock it down very effectively, if they really wanted to.
Without any inside knowledge, the only things we know for certain are that they are not so concerned about it that they are in any hurry to change the current situation (from which we can probably reasonably infer that a framerate hack is probably not viable) , and that they have sold a number of additional units that they wouldn't otherwise have sold as a direct result of hackability.
If anything, I suspect Fluke are more pissed off than Flir.