The West of England 10 Year Rail Delivery Plan for Investment: 2020 - 2030 (see
http://www.firstgreatwestern.info/coffeeshop/index.php?topic=24296.msg297475#msg297475) has the following:
Severn Beach to Bristol Temple Meads and Westbury enhanced service
3 TPH▸ Severn Beach to BTM▸ [sic]
4 TPH Bristol Temple Meads to Westbury
Bristol Travel to Work CMSP [Continuous Modular Strategic Planning]
Line doubling between Montpelier and Filton.
Double junction at Holesmouth.
Platform capacity at Severn Beach.
Resignalling Severn Beach Line.
Westbury to Bath corridor capacity works.
Potential for new Saltford and St Annes Park stations
This is listed as 'low deliverability' with a timescale of 10-25 years.
It took me a moment to understand 'Line doubling between Montpelier and Filton', but presumably they mean that the whole of the 'Beach line would be doubled except for the Narroways - Montpelier section. Interesting!