Speaking broadly, there is nothing that may lead to a near-term treatment other than the ongoing Rituximab phase III trial.
If this is found to be useful, and safe in CFS, then it may be available relatively quickly.
https://clinicaltrials.gov/ct2/show/NCT02965768 Nalotrexone is another possible treatment, though I understand the results to be less clear than rituximab.
As to 'mechanism', there are a lot of 'this is weird' papers - but there is no mechanism for why CFS happens. In order for drugs to be developed specifically for CFS, a mechanism and then a point to attack the disease with a drug needs to be found.
It seems unlikely this would happen before 5 years, with a designed treatment at least 15-20 years away.
http://www.fdareview.org/03_drug_development.php is informative.
There are several stages before this that need to be done first, which have not been done for CFS.
Work out mechanism for disease.
Work out drug target to interrupt or reverse mechanism of disease.
Develop compound(s) as candidates for doing that.
Only then do we get to the left of that diagram 'toxicology', and then it's about 20 years, and 12 tested compounds and many hundreds of millions of dollars typically to to get one working drug out.
(on average, it may turn out that the approach used does not work at all).