First, Mirrorless is not equal to Micro 4/3. There are many current and emerging systems; NEX, NX, etc... a few more are "rumor" status. Canon, Nikon of course. Leica just announced a mirrorless system for 2012 Photokina. Fuji is rumored to toy with interchangeable lens capable version of the X100. Pentax just released the weird and yet to be proven practical Q system.
Second, no way to tell.. do you have a magic crystal ball? If I could predict product decisions like these, I can make loads of money in investments.
Third, don't spend too much energy worrying about these things...... its not like camera equipment (except a few exception) "appreciate" in value... they are an expense. If I said yes... in the near future all your stuff is obsolete, what would you do now? If I said no.... what would you do differently?
Think of it this way:
Canon FD lenses became obsolete... and it had nothing to do with another format but a manufacturer decision.
On the other hand....
4/3 (non-micro) SLR lenses do NOT become obsolete..... they are functional (AF, metering, stop down) on micro 4/3... also a manufacturer design decision.
On the other hand....
Ricoh just purchased Pentax... its possible that will be the end of it for older K-mounts... a business decision.
On the other hand...
Nikon, Pentax and Leica for example have maintained backward compatibility for decades of lenses....
On the other hand...
Maybe mirrorless will just die off (personal opinion... it won't)... market acceptance
On the other hand...
Leica left R-system SLR users behind when they discontinued the R systems + digital module.
On the other hand....
What if the earthquake just wiped out Japan's ability 100%.... Let'see.. Canon, Nikon, Panasonic, Olympus, etc.. all gone... and we've got bigger concerns.
On the other hand..................... (goes on and on).
Your head will spin because the answer is unknown.