In August 2015, Network Rail published their Wessex Route Study. This identifies the options for infrastructure improvements required to support passenger and freight growth on the rail network over the period to 2043 and forms part of Network Rail's Long Term Planning Process.
The Wessex Route Study includes a number of proposed rail capacity improvements on main routes to and from London and within the Solent area. These include additional platforms at Southampton Central and potential electrification of the routes to Salisbury from Southampton and Eastleigh via Chandlers Ford.
More importantly, Network Rail has committed to working closely with Solent Transport and other local stakeholders to study the need for enhancements to East to West rail connectivity, in support of planned economic growth and housing in the Solent.
Full details of the Wessex Route Study can be found here