If there will be no troops and forces from the West (US, UK, EU or NATO), coming to their rescue, I anticipate that the Russians will have a walkover of Ukraine within the next 2 weeks. The Ukrainian forces are simply outnumbered by the Russians. Unfortunately, this scenario is getting more and more likely by each day.
Economic sanctions are not going to do much harm to Putin and his gang. History has shown that Iran, North Korea and Cuba all have sanctions for so many years already, but they are still as capable as ever in their military arsenals procurement.