Roadmaps to Unicode lists the blocks that are in the process of being added to Unicode; the approval process needs to be sync’d with ISO, for those countries that prefer a non-commercial standard, and takes a few years.
The green blocks as of this writing, which are the furthest progressed, are:
- In Plane 0 Syriac Supplmental: http://www.unicode.org/L2/L2015/…, Cyrillic Extended C: http://std.dkuug.dk/JTC1/SC2/WG2…
- In Plane 1: Osage, Newa, Mongolian Supplemental, Dogra, Zanzabar Square, Soyombo, Bhaisksuki, Marchen, Masaram Gondi, Gunjala Gondi, Makasar, Tamil Supplemental, Medefaidrin, Ideographic Symbols and Punctuation, Tangut Ideographs, Tangut Components, Nushu, Glagolitic Supplemental, Adlam, Indic Siyaq Numbers
- In Plane 2: CJK Unified Ideographs Extension F
Unicode won’t add extended blocks just because it can. My area of expertise, such as it is, is Greek, and I was explicitly asked by Unicode to check that there was nothing else left to include. There will not be a Greek Extended-B.