A recent blog notes that the 8.1 update will be free and available through the Windows Store.
Look out around the 26th June for a public preview:
Ref:
Link Removed
applications
consumer experience
continual updates
dell xps 12
development conference
device choice
free update
game apps
lenovo yoga
mobile computing
new features
oem partners
performance update
publicpreview
sony vaio tap
tablet experience
touch experience
windows 8
windows 8.1
windows store
The Verge has revealed more details on the Windows Blue release:
Reference:
Windows Blue public preview planned for Build developer conference | The Verge
announced plans
applications
build conference
developer
early preview
features
leaked build
microsoft
milestone build
oems
publicpreview
resolution limit
screen sizes
side-by-side
snap view
upgrade
user interface
windows 8
windows blue