Let's make some assumptions - Scotland is going to distance itself from England and Wales over the next five years whether that be by moving to fiscal independence first or complete independence (are they different propositions?).
The House of Lords is not going to be reformed but an unelected House is no longer appropriate.
Four lower Parliaments - England, Wales, Scotland and Northern Ireland - with equal powers but bound together by a UK Senate (which is what the House of Lords becomes). The Seante might be responsible for the Environment, some elements of Treasury, Transport and Foreign Affairs, otherwise all would be desolved to the lower Parliaments.
The more Scotland clamours for more independence the more the English will start to ask if them why not us?