With Russian WTO entry their companies will have a hard time (at first) competing with Chinese, Indian and Western companies. It is more likely, at first, to increase foreign investment and force them to sort out their red tape and corruption issues, as otherwise the investments become too high risk. Short term for their own food and industry companies they are unlikely to find alot of export markets as by and large they are not competitive. It would make sense for a slight devaluation of the rouble until these competitiveness and other issues are dealt with. However thanks to it's gas and oil resources Russia runs a surplus and is has money to spend (they were asked to buy into the EFSF). They could, if they chose, defend the value of their currency with their reseves or just by marginaly increasing the cost of gas.
Ukraine we have discussed before privately and I pretty much agree that a default is likely here, but they will just have an IMF renogiation and the default will be 'structured' a la Greece with more bank refinancing in Europe and elsewhere. Presumably some Ukrainian banks will fail and become 'nationalised'. In many ways Ukraine is another Greece/Italy outside the system so it retains the option to print/devalue it's way out of the corner. Again though Ukraine has similar uncompetiveness and official corruption issues as Russia (I could tell you an amusing story about this).
Belarus I know little about but assume ultimately until they get rid of Lukashenko they will become a Putin fiefdom, dependant on the Czar for whatever meat he choses to throw them from his High Table. Certainly they are likely to take part in Putins "Eurasian union".
Poland is formaly pledged to join the Euro at some undecided time and if it still exists. Unlike the others HAS cut alot of the 'red tape' and dealt with some official corruption. It has also benefitted from alot of inward investment and it's industry and agriculture are 'European competitve'. They might even be about to get rid of the hideous 'Palace of Culture' (http://www.chrisputro.com/russia/117...%20Science.JPG) outside Warsaw station. About 70% of Polish exports and imports go and come from/to EU countries. "Polish trade is dominated by the EU--around 60% of its imports and 80% of exports come from or go to EU member states" Poland
Looking forward Poland is also reckoned to have one of the largest deposits of shale gas in Europe; Shale Gas in Poland Sparks Hopes of Wealth, Energy Security | Europe | English
Poland is firmly locked into Europe short term and long term the Visegrad Group offers other options should the Euro/EU collapse. I cannot see a Ukrainian default or a Russian devaluation harming Poland much.