Many people have already had their channel maps changed. I haven't had ANY of mine changed (3 receivers) but it's supposed to be done this week. And of course the channels will be re-routed to their new homes on other satellites.
It is absolutely wrong to say all Shaw Direct channels "south of the border" will disappear. Channels on G1 have never been receivable "south of the border" - it's just going to be a different set after this week.
Almost all standard definition channels will be gone in a few days.
If you have the obsolete LNB, you may experience some further channel loss, but if you upgraded to the xKU LNB, all the changes should be over in a few days. I must admit that my knowledge of the obsolete LNB is limited because I'm not interested - I upgraded years ago.