Have Russian Drilling Operations in Lake Vostok Succeeded Yet?
The Russians did "succeed" to reach the water at borehole 5G-2 in 2012. However, the lake water flooded into the borehole due to overpressure, and refroze. They drilled again during the next campaign to sample this refrozen lake water, but found that it was contaminated by drilling fluid (DF). From Alekhina et al. 2017:


  As expected, the level of contamination of the frozen water core with the DF constituents decreases as the depth of sampling increases. However, even in sample 3450, the deepest and cleanest of all those studied, the concentration of foreign organic compounds (16.7 mg l−1) indicates significant chemical contamination, especially for water as pristine as that which we expected to obtain from Lake Vostok [...] After the rising water in borehole 5G-2 reached the junction of the two boreholes and continued to rise in 5G-1, the drilling fluid that remained trapped in the abandoned borehole began to be displaced by the heavier water. As a result, about 1 t of DF rose from the bottom of 5G-1 to the top of the lake water column that had already filled the borehole. During this process, the rising DF mixed with, and thus contaminated, the freezing water.


Because of this contamination, any biology result from these ice cores would be invalid for the scientific community. After that, the Russians have drilled a new borehole (5G-3) where they allegedly managed to sample pure, uncontaminated water in 2015 (here is the press release from RT, which is not considered a neutral source...). However, I could not find any published results from this sample. And the same year, Russia cut Vostok project's budget... So I doubt we will see anything coming out of this in the future.

On a more positive note, scientists did manage to drill through 800 meters of Antarctica ice to reach another lake, lake Whillans, without contaminating it (they used only hot water to drill, not drilling fluid). And they did find "a diverse assemblage of bacteria and archaea". From Christner et al. 2014:


  Our data show that SLW supports a metabolically active and phylogenetically diverse ecosystem that functions in the dark at sub-zero temperatures, confirming more than a decade of circumstantial evidence regarding the presence of life beneath Antarctica’s ice sheet [...] Given the prevalence of subglacial water in Antarctica, our data from SLW lead us to contend that aquatic microbial ecosystems are common features of the subsurface environment that exists beneath the ~10$\small\mathsf{^7}$ km$\small\mathsf{^2}$/s Antarctic ice sheet.


However, there is a major difference with lake Vostok: lake Whillans is connected to a hydrological system, while lake Vostok is "closed" and has a water residence time of over 10,000 years. So if life is trapped in there, it could have evolved differently...