No official specs are given so this is only based on player comments.
Release date: On RU forum SerB wrote ( "confirmed" ) that new T10 MT & TD will be released in 7.5 patch so that will put it some where around 09.2012 ( give or take a few months knowing WG )
EXP: Overlord wrote that we can expect same amount of exp for T10 MT & TD as for HT so around 180-220k will be needed ( maybe even more )
COST: Since T10 HT are at 6M we can expect that new T10 MT & TD will also be priced at this rate so around 6M.
1. Tier 10 medium tanks
Some facts about this tank are explained at this post:
In short it will pack 100mm gun D-54TC and not the
115 mm U-5TS
smoothbore gun as some players have stated since this is T-62A not T62.
T-62 was a developed from T-55 and was produced from 1961, while T-62A is apredecessor of T-62. It was essentially a stretched T-55 with some improvements.
GERMAN: E-50 Ausf M
Some blueprints ( don't know if they are accurate )
Here we can expect same thing as current E-50, maybe some better armor but gun is the same. It will have some "advantages" like rear engine and transmission ( since they are nerfing current E line by moving transmission to front we can call this a buff or just pre 7.4 E-50 ). It will have it's turret moved to front a bit so it will have some advantage at peekaboo game play.
USA: Patton III
Some posts speculating what it will have:
In short we can expect better accuracy, rof and/or dmg from the new gun. Possible improvements could also include better speed and mobility and armor. We will have to wait for official specs.
FRANCE: BatChat 25t
Well we all know this tank, those who have it love it and those who face it hate it....
All french tanks starting at AMX 12t will be moved tier up and new ELC AMX will be french T5 tank.
At Bat we can expect better gun, mobility and/or speed. In short new CW scout, in "expert" hands death on wheels.
2. Tier 10 tank destroyers
USSR: Object 268
Some player info on it ( not official ):
From this tank we can expect better frontal armor, better mobility. New gun but for it's specs we will have to wait.
GERMAN: JagdPz E-100
Some player info:
Technically speaking this should be a beast, 17cm gun, E-100 chassis. It should be able to one-shoot anything up to T8 ( with penetrating shoot ), but this only my opinion and we will have to wait for WG to know the reality.
We can expect slow turning, slow rof, high dmg, high value armor.
USA: T110E3 & T110E4
Some player info/posts:
T110E3 will pack same gun as T95 155mm At gun T7. Armor will be same as on T95 or less ( if less we can expect better mobility, speed ). It could have better rof, and overall speed. ( They should have placed T95 as T10 and T110E3 as T9 )
T110E4 same gun as T30 155mm At gun T7. It will have partially rotating turret 180 degrees. What to expect I don't know perhaps better rof, mobility and higher hull armor.
France: AMX 50 Foch
Some player posts:
Since french TD tree is not yet released ( only on test server ) I don't know what to expect with this tank. From what we know french TD same as HT and MT line has high speed, great mobility, paper armor and auto-loaders and this T10 TD will have one. We can expect 3 fast shots ( enough to kill a T9 or seriously damage T10 if all pen since avg dmg is shown for T9 to be at 300-500 and pen 200-334 ) and after 3 shots are made a 50-60 sec reload time.
There is no news on release date of British tanks.
German Leo 1 according to Overlord will be released in the future ( some players speculate that it will be second MT line continuing VK 3002 (DB) ), not sure if that is correct but only the time will tell.
There is also some speculations that 7.5 patch could bring some buff to E line ( E-100 ) if the rumors are any true this is a good news, but we will have to wait.
What I would like to see in the future is a Tier 10 arty .