Not only is there a G5 coming, but also a G7 and an MX610. It looks like they are separating the lines into Gx for gaming and MXxxx for the cubicle bound soul-sucked office troglodytes. Personally, I just want a Marble Mouse with a scroll wheel, but if I ever get $99 to my name, the Kensington Expert Mouse looks really nice.
So, what are they? Well for the G5 look here, and a PDF is here. The G7 is found here, with the PDF here. Last but not least, the MX610 is here and the troglodyte pleasing PDF is here.
The short story is that the G5 is an MX518 with 2000/1200/400DPI adjustable resolution and laser instead of LED tracking and the G7 is the same thing in cordless variety. The MX610 has nowhere near the rez, it looks to be just a cordless MX510. This is not a bad thing however, the MX510 is an amazing mouse, and Logitech is one of the best at removing cords without removing performance or mysteriously killing all the bats in the neighborhood when you power it on. They will sell for 59, 79 and 43 Euro respectively.
This is a solid lineup, none of them look at all bad, and the fact that they all are laser is a good trend. Laser mice coming down in price makes life better for end users, it is a better way. For me, the G5 looks to be the one for the masses, not all that expensive, and no batteries to die on you. ยต