The next will happen some time after the current lawsuit which, for the Californian case at least, should be resolved over the next few weeks/months.
Currently, however, overall, XenForo is secure and stable. In terms of any features you consider to be missing, these can often be catered for by the hundreds of add-ons in the Resource Manager.
Not every forum product has to release an update every few months.
There are some outstanding bugs, but none that are particularly troublesome or don't have a work around.