There's no definite meaning for "R" - it's shown as "Return"/"Rebirth"/"Reborn"/"Rally" and many others in one of the scans below.
The story will be in UC0089, with the display of information and records from E.F.S.F.'s Federation Survey Service department - information regarding undisclosed MS from the past of course.
We'll be getting a new MS in next month's issue of Gundam Ace: MS-06G Ground Combat High Mobility Type Zaku. ^^
Could this be the next HGUC project as well?
Others:
Robot Damashii releases:
* Exia - July release, 2,625 Yen (inclusive of tax).
* O Gundam - May release, 2,625 Yen (inclusive of tax).
* Masurao - Late July release, 3,360 Yen (inclusive of tax).
* Empruss - Release date & price TBA.
* Ahead Smultron - April 18th release, 2,625 Yen (inclusive of tax).
* GN-X III E.S.F. Color Type - April 18th release, 2,625 Yen (inclusive of tax).
* Garazzo [Healing's Unit] - June release, 2,940 Yen (inclusive of tax).
* Gadessa [Healing's Unit] - May release, 2,940 Yen (inclusive of tax).
* Crossbone X-1 - Late June release, 3,150 Yen (inclusive of tax).
BB Senshi Sangokuden:
* Kochu Gundam Mk. II - April 16th release, 630 Yen (inclusive of tax).
* Bacho Blue Destiny - Already released, 630 Yen (inclusive of tax).
* Daitaifu Shiba-I Sazabi - Already released, 1,050 Yen (inclusive of tax).
* Koumei ReGZ & Shuuyu Hyaku Shiki The Red Cliff Special Set - Already released, 1,260 Yen (inclusive of tax).
* Sonken Gundam & Shuuyu Hyaku Shiki 赤壁之轟砲 - Already released, 1,680 Yen (inclusive of tax).
* Soldier Unit - April 16th release, 420 Yen (inclusive of tax).
* Joko Serpent - May release, 630 Yen (inclusive of tax).
* Sonshoko Gerbera - May release, 630 Yen (inclusive of tax).
YAMS-132 Rozen-Zulu from Gundam Unicorn:
Development of the world after the ending of Gundam Double O Season 2 Episode 25 (I think):
All scans from CyberGundam.