They will fix two specific issues: 1) an HMAC ABI incompatibility with previous releases, and 2) make it possible to accept a zero length extension block in a ClientHello.
To clarify, the mentioned HMAC ABI incompatibility occurred in recently released versions 1.0.2b and 1.0.1n which are security fixes but which may cause other problems due to the ABI issue. Therefore, the forthcoming releases should be used in preference to 1.0.2b and 1.0.1n.