Rumourmongering notwithstanding, the answer is I don't know.
I don't know how sophisticated the NHL's testing protocols are, and with the IIHF opposed to the WADA protocols of athletes having to provide their whereabouts on a 365-day basis (the IOC wants this, and team sport federations IIHF, FIBA, and FIFA are all opposed), there are, potentially, opportunities.
With Washington's roster, they will have several members of their team likely playing in the Olympics, which has tougher testing standards than the NHL (among other things, a lot of OTC cold medication will register a positive test).
I'm not sure about steroids. Other PED's like HGH and EPO, which help with recovery...without knowing how sophisticated the testing is, it's hard to answer the question.
I'll say this- "if" (and without factual evidence I don't like accusing someone of something) NHLers were to be using PED's, I'd say things like EPO and HGH are the most likely options (given the rigours of their season and the marathon that is the playoffs). The league can, and should, test players throughout the season, including the playoffs.
With that being said...it's a joke what North American sports leagues punish drug cheats for when you compare the penalties outside of North America. Roughly a suspension of 1/4 of a season in North America, while team sports (rugby, soccer) have 1-2 year bans for a first time offence. If the NFL, NBA, MLB, and NHL were to be serious, a 2-year ban for a positive test would indicate a level of seriousness.