Over the past 20+ years Manchester has put all its eggs in the Metrolink basket and there has been comparatively little investment in what you could call suburban rail. Mayor Burnham's plan is to carry on with this, e.g. proposals to convert existing heavy rail lines to trams or to deploy tram-train technology.
The contrast with other big regional cities in the UK is interesting: e.g. Bristol, Leeds and Birmingham all have plans to re-open heavy rail lines and/or re-open stations that were previously closed or build new ones. e.g. there are advanced proposals to build 4 new stations in Leeds, maybe 7-8 in Birmingham/Black Country, 4-5 in Bristol and at least 2 in Liverpool.
By contrast, I am can't off the top of my head think of any advanced proposals to re-open any closed railway stations in the Greater Manchester area. Manchester now has the dubious distinction of having the least used railway station in the whole of Great Britain (Denton).
Train services in Manchester are currently crippled by under-investment in capacity. As a result it is very likely that services through Piccadilly P13/14 will have to be reduced by 2 trains per hour to improve reliability.