Most dealmakers expect an increase in M&A activity in 2015 but not on the scale of the blockbuster activity of 2014, according to Brunswick Group.

Brunswick queried 115 top M&A advisors around the world for its annual study, finding 54% forecast an increase in deals for this year.

Brunswick US senior partner Steve Lipin said dealmakers have "high hopes" for 2015 but are less bullish about eclipsing 2014's $3.5 trillion tally. Lipin said increased influence by activist shareholders will likely mean more divestitures, break-ups and spinoffs, in addition to sales and acquisitions.

Sixty-two percent cited activists as the top factor driving M&A in North America, while 73% see shareholder activism increasing in the region this year. Brunswick notes that only 28% cited activists as main drivers of M&A in 2012.

A byproduct of the activism could be increased engagement between boards and investors as 85% dealmakers polled by Brunswick see this result. Compared with 2014, dealmakers see an increase in M&A demands by shareholders (11%, up from 3% in 2014) , a slight dip in spinoffs, sales or divestitures (34% from 39%) and a slight increase in activist demands for board seats (28%, up from 27%).

The most active sectors for consolidation are seen as healthcare (65%), energy (59%) in North America, and technology/telecom (81%) and healthcare (75%) in Europe. Asian dealmakers are focused on consumer goods and retail for consolidation this year.