First preorder option are now available in Europe too. Feel free to add more proerder links by commenting this post.
Olympus Europe:
E-PL8 at Amazon.de.
25mm f/1.2 PRO at Amazon.de.
12-100mm f/4.0 PRO at Amazon.de.
30mm macro at Amazon.de.
FL-900r flash at Amazon.de.
Panasonic Europe:
G85 at ParkCameras. WexUK.
FZ2500 at ParkCameras. WexUK.
Lx10 at ParkCameras. WexUK.
Olympus USA:
E-PL8 at BHphoto, Adorama, Amazon, GetOlympus.
25mm f/1.2 PRO at BHphoto, Adorama, Amazon, GetOlympus.
12-100mm f/4.0 PRO at BHphoto, Adorama, Amazon, GetOlympus.
30mm macro at BHphoto, Adorama, Amazon, GetOlympus.
FL-900r flash at BHphoto, Adorama.
Panasonic USA:
G85: BHphoto. Adorama. Amazon.
FZ2500: BHphoto. Adorama. Amazon.
Lx10: BHphoto. Adorama. Amazon.