The etymologies for talon and mushroom are not completely settled, but in both cases it seems clear that the Middle English word (talon or mussheron) was imported (from Old French) in its full form:
- the Old French talon comes from Latin talonem, from talus (my French Littré qualifies talonem of “fictious form of talus”, etymonline calls it “Middle Latin”).
- mussheron is reported to come from Anglo-French musherun, “perhaps from Late Latin mussirionem”
As such, it doesn't seem logical to consider -on or -eron as English suffixes. At least, not on the basis of these two examples.
There is one modern use of -on as a suffix, which is unrelated to your question as I understand it, in science. The New Oxford American Dictionary says:
-on (suffix, Physics, Biochemistry & Chemistry, forming nouns)
- denoting subatomic particles or quanta: neutron, photon.
- denoting molecular units: codon.
- denoting substances: interferon.