I must to said, there is no chance to see ram slots
No chance for a new form factor if they simple quietly update the mini
The current form factor is built around the ability to upgrade RAM through the bottom cover. Thus sticking with the same form factor would imply upgradable RAM or conversely, soldered RAM would imply a change in form factor. Apple is not going to keep a removable bottom cover for no reason.
a new form factor will be announced at am media event at least, it's what deserves.
A new Mac Mini could be announced at the Sept. 9th event. So there could be a new form factor or not... We just don't know yet.
About Thunderbolt, rMBP comes with TB2, coz it's part of the Haswell chipset
Not true. TB2 requires an extra "Falcon Ridge" chipset. So while a new Mac Mini might include TB2 it won't be coming along for free. My only concern is that the price point of the Mac Mini won't allow for something like this whereas the MBPs and iMacs selling at over double the price have more margin buffer.
Hdmi port has no risk, as the rMBP users cry for an extra usb3 instead hdmi Apple kept the hdmi port.
I hope you're right, although my fear is that a redesigned form factor might put pressure on the number of ports, and HDMI might give way to more versatile TB ports instead.
The bottom line is since there will no longer be a server model there will no longer be a need to service the Mini and therefore it will be sealed, glued and soldered.
I would expect a server model to continue if the form factor remains the same. If they change the form factor to something more compact, you're probably right.