This page tracks potential future work of the HTTPbis WG, including new features and already-used features that need standardisation. Inclusion on this list is not a guarantee (yet) that we'll work in this area; it's just input to possible future re-chartering.
Most UAs implement a "Refresh" response header that instructs the browser to refresh its view. Standardising this (possibly with advice on when NOT to use it) is probably necessary.
Increasing precision of Last-Modified header to allow sub-second granularity
It would be nice if the Last-Modified header could (optionally) carry more precision that one second, for the benefit of clients that wish to reliably detect when a server has changed its output faster than once per second. For example:
Last-Modified: Fri, 27 Jan 2012 20:21:10.011483 GMT
Note that it is possible to get around the current one-second limitation using ETags, but it would be more convenient if this could be done directly in the Last-Modified header, because: (a) clients would know that it is a (high-resolution) last modified time as opposed to an opaque string in an ETag; and (b) servers would not have to set both the Last-Modified header and the ETag header when simply trying to indicate a high-resolution last modified time.
This is relevant to high-speed distributed systems that are based on HTTP.