Don't get hopes up around ADS-B. In the US for CAT and high altitude flight it is just Mode-S ES with GPS/FMS fed extended squitter - and this is what Europe has indicated it will go for. The US (lobbied extensively by AOPA) are also going for ADS-B based on UAT, which will provide greater bandwidth and allow uplinking of weather METARS, etc (i.e. the same stuff they up link with TIS).
So, going to ADS-B probably will mean, a software upgrade to your Mode-S transponder, and approved GPS for position data (maybe Galileo with a megaŁ subscription just to p!ss people off
, and maybe some major mod paperwork.