Just seen on a rail related forum that the National Railway Museum plan is to return Mallard to steam for a period starting around 2036 so she is mobile for the 100th anniversary of her record.
I cannot vouch for the accuracy of the information but apparently it is in the long term plan that the NRM have for which of their locomotives will be in steam when.
If I have any point to make I think its that there are a variety of levels of condition and treatment between 'Static' and 'Working', in this case the NRM seems to have opted for 'Static with periods in steam for important anniversaries' - which is close to what a lot of locos end up with by default anyway.
Things go all the way from the coach the NRM have kept in 'as recovered from a garden' state, though the Loch Ness Wellington 'as found on bottom of lake, with additional protection' through 'static but parts in motion due to electric motor or compressed air', 'completely new build to old plans, with modification' (Tornado) and even 'still under some active development' (many of the Ffestiniog Loco's - e.g. the fitting of 'Gas Producer' fireboxes, use of hoses rather than ball joints on the Fairlies etc.)
Dare I say it, the plan for Mallard is quite like the plan for K7, as I understand it, with the exception that the work to get K7 running will be less (de-inhibit rather than build new boiler etc.) and K7's running periods will be shorter but more frequent.