If you have to ask that question, then perhapse it is not worth it.....but....
How worn out is your second edition? pieces missing?
You have a few expansions but not all. Rev4 will probably come out with all the same expansions again does that interest you?
Do you play a lot of talisman? couple times a month or couple times a year?
Can you go with skipping the purchase of a few video games for a talisman board?
Do you have only $100 bucks in your bank? or thousands?
Did you see the re-release of Starwars a New Hope in the theater, even though you have seen the movie over a hundred times?
Are you a collector?
The question you asked about purchasing REV4 is one only you can answer.
I for one, Own 3rd edition, and the Black Industries 4th edition. I purchased the FFG REV4 as well.
but thats just me. I am not you.