Well if India, Bangladesh, Afghanistan and Bhutan back out. There will be no summit in Pakistan.
Lastly, in case you have a short memory (which I am sure you do), you would know that last time the only country blocking proposals that everyone wanted - was Pakistan.
In fact, every country in SAARC was so miffed at Pakistan, they went ahead and signed the same agreements with each other bilaterally.
That is how the entire SAARC views Pakistan. An obstacle and an outlet of foreign powers standing in the way of South Asia.
How?
Once again, you show your reduced intelligence. SAARC is for South Asian countries. SCO is not.
Bangladesh, Sri Lanka, Bhutan, Nepal are not in SCO. Ergo, it cannot be a replacement.