Although the importance of the trend component has fallen markedly since the 1970s, the estimates produced by Stock and Watson suggest that it is still large enough to be economically meaningful. The bottom panel of figure 2 illustrates this point; as you can see, the estimated trend (the solid line) has drifted up a bit since the mid-1990s.
Of course, such estimates are inevitably imprecise to some degree. For example, Cecchetti et al (2007) employ a slightly modified version of the Stock-Watson procedure in a recent paper and find that inflation persistence has fallen so low that their estimated trend for gross domestic product (GDP) price inflation has been almost perfectly flat at about 2.2 percent over the past few years.