I changed the bootstrap.less file ( templates/t3_blank/less) in line
// Components: Popoversnew
@import "../../../plugins/system/t3/base/bootstrap/less/modals.less"; old <------- changed by-----> new @import "../../../plugins/system/t3/base-bs3/bootstrap/less/modals.less";
and changed name de bootstrap.less file by bootstrap3.less. I also created a theme for me with all the files. Bootstrap css 2, but I changed the codes from the modal bootstrap2 by boostrap 3 in my theme.
I can upgrade without problems ?
I have new t3 plugin installed with t3_blank with bootstrap 2.
I started using joomla to 4 months, and then I met T3 framework, I saw it was a great base to work with. Easy to use and customize.