3) What will be the trade policy for licensing? It is expected a low cost to those who own a previous version?
Sencha does not provide us with discounted upgrade licenses to Ext JS, so unfortunately we have no discount to pass onto our customers. The final Ext.NET 4 pricing (new and upgrade) is yet to be determined, but at the moment it appears it will be the same as Ext.NET 3.
If you have a valid (non-expired) Premium Support subscription, upgrading to Ext.NET 4 will be $2499 USD. As a new customer or without a valid Premium Support subscription, upgrading to Ext.NET will be $3499. These prices are subject to change at any time.
Our plan is to release Ext.NET 4 immediately after the availability of Ext JS 6.1.
Hope this helps answer your questions.