It's even worse than that, from section 10 (Concluding Remarks)

…In the long run, we believe that these patches are ad hoc and that new attack vectors will continue to emerge. Current systems are fundamentally insecure un- less speculation is disabled. However, we believe that it is possible to design future generations of CPUs that re- tain speculation but also close speculative leakage chan- nels, for example by keeping speculative data in separate CPU structures than committed data.