Hi Becky,
I'm more of a magnetospheric physicist, so I don't know a lot about what new solar physics missions are currently in development. However, I do know about some of the missions currently in development to study the Earth's magnetosphere. Scientists and engineers working in the Department of Physics and Astronomy here at the University of Iowa are currently building the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) experiment for NASA's Radiation Belt Storm Probes (RBSP) mission, which will be launched in May 2012. You can learn more about RBSP here: http://rbsp.jhuapl.edu/index.php
Other scientists here at the University of Iowa are involved with developing instruments for NASA's MMS-SMART (Magnetospheric Multiscale - Solving Magnetospheric Acceleration, Reconnection, and Turbulence) mission. I am currently running computer simulations to help the instrument team at the University of New Hampshire calibrate the Electron Drift Instrument (EDI), which is part of the FIELDS investigation on MMS-SMART. The MMS-SMART mission will hopefully be launched in October 2014. You can learn more about the MMS-SMART mission here:http://mms.space.swri.edu/index.html
Kris